Concrete slipform pavers are known. Specifically, such pavers include a "tractor" and a "paving kit".
Regarding the tractor, most concrete slipform pavers include a tractor which is comprised of a rectilinear frame which straddles the concrete roadway or runway while it is paved. This frame is propelled and supported on either end by side bolsters and crawler track(s). The frame supports a diesel engine driven hydraulic power unit which supplies power to the tractor and paving kit.
The paving kit is typically suspended below the tractor frame by mechanical means. The paving kit takes its hydraulic power from the power unit on the tractor. The tractor and paving kit comprising the slipform pass over the concrete placed in its path in a relatively even and level mass that can be conveniently paved. During this slipform process the tractor attached paving kit spreads the concrete dumped in the path of the paver, levels and vibrates it into a semi-liquid state, then confines and finishes the concrete into a slab with an upwardly exposed and finished surface. Sideforms mounted to the side of the slipform kit confine the sides of the slab during the paving process.
The tractor typically has either two or four crawler tracks supporting and propelling the frame and attached paving kit. Other kits can be attached to these tractors such as kits for conveying and spreading concrete and trimming and spreading base materials. For the purposes of this description, we will focus on the paving kit used for slipform paving.
With respect to both two and four track pavers, the tractor frame is known to telescope itself normal to the direction of the paving movement. This telescoping normal to the direction of the paving movement enables the tractor frame to span different widths of pavements within the limits of the telescopic extensions. Once these telescopic extensions limits are reached, a fixed frame extension can be added to one or both sides of the telescopic frame for further extension. Despite the telescopic ability of the frame, the process is still a relatively complex and time consuming operation. Adding a fixed frame extension(s) significantly increases the complexity and difficulty of the frame width change.
Regarding the addition of the fixed frame extension, this addition requires that the side bolster and crawler(s) on at least one side of the machine be removed, the fixed frame extension inserted, and the side bolster and crawlers reattached. Hydraulic and electrical lines must also be disconnected then reconnected. This is not a trivial operation. The frame section and side bolster/-crawlers are heavy members. They must be separately manipulated into place--usually by cranes and their attendant crews. Cranes have scheduling problems, are big, heavy, dangerous, and slow.